Fluid delivery system utilizing multiple port valve

ABSTRACT

The present invention is directed to the implementation of a multi-port rotary valve in an automated chemistry processing instrument which reduces chemical reagent cross contamination and simplifies system design and control. One or more multi-port rotary valves are used in conjunction with isolation valves which are each dedicated for an associated reagent in the system. According to one embodiment of the present invention, the instrument utilizes a multi-port valve which defines several fluid branches each associated with a reagent. The valve has a common inlet and common outlet which are selectively brought into fluid communication with the branches in a controlled sequence. At each branch, there is a two-way three-port isolation valve which controls introduction of an associated reagent into the branch. When a branch is selected by the rotary valve, the reagent introduced into the branch is delivered out of the common outlet by the flow from the common inlet. According to another embodiment of the present invention, the reagents are introduced through isolation valves between two multi-port rotary valves.

The present application is a continuation of U.S. application Ser. No.07/909,232 filed Jul. 6, 1992, now abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to fluid delivery systems, and moreparticularly to multiple port fluid delivery systems for use inautomated chemistry processing instruments.

2. Description Of Related Art

For fluid delivery systems designed for handling several types of fluidsin a flow system, one of the design concerns is to reduce crosscontamination between the fluids. Especially for systems handlingchemical reagents, cross contamination between different reagents oftenadversely affects the chemical integrity of the reagents and thus theefficiency of the controlled chemical reactions that involve suchreagents. For example, in an automated nucleic acid synthesisinstrument, various steps are carried out by a reagent delivery systemwhich dispenses a number of chemical reagents in a predeterminedsequence in a cycle into a synthesis reaction column, in accordance withinstructions from the system controller or computer. The synthesisefficiency depends in part on the integrity of the reagents.

As a background, the chemistry of nucleic acid synthesis (generallyreferred to as "DNA synthesis") is well known. Generally, this is theprocess of constructing synthetic single-stranded oligonucleotidethrough linking of various nucleotides which are the basic buildingblocks of DNA. DNA synthesis is described generally in U.S. Pat. No.4,458,066 issued to Caruthers et al, entitled "Process for PreparingPolynucleotides", which is incorporated by reference herein. The processdescribed therein constructs a single-stranded oligonucleotide using oneof several approaches in synthesizing DNA, namely the so-calledsolid-phase phosphoramidite method which generally involves the steps ofdeblocking/activation, coupling, capping and oxidation in each synthesiscycle for linking a building block on a solid-phase support. Furtherreference to this process of DNA synthesis may be found in"Oligonucleotide Synthesis - A Practical Approach" edited by M. J. Gait,IRL Press, 1984, which is incorporated by reference herein; and inparticular Chapter 3 therein entitled "Solid-Phase Synthesis ofOligodeoxyribonucleotide by the Phosphite-Triester Method" written byTom Atkinson and Michael Smith. It is suffice to understand for purposeherein that the reagents are delivered to the reaction column viaseveral valves.

The effectiveness of the DNA synthesis process is very sensitive to thepurity of the reagents. Cross contamination between the reagentsadversely affects the production of oligonucleotide. One source of crosscontamination is in the valves, particularly multi-port valves whichselect delivery between different reagents. There are inevitable deadvolumes in the valves associated with switching between reagents. Forthis reason, past instrument designs which have required absolutecontrol over cross-port contamination and random selection of chemicalreagents have avoided use of multi-port valves because of thedifficulties in preventing such contamination. However, the adopteddesign of the fluid delivery system is relatively complex and requiresadditional effort in designing the control scheme for the system.

SUMMARY OF THE INVENTION

The present invention is directed to the implementation of a multi-portrotary valve in an automated chemistry processing instrument which isconfigured to reduce chemical reagent cross contamination and simplifiessystem design and control. One or more multi-port rotary valves are usedin conjunction with isolation valves which are each dedicated for anassociated reagent in the system.

According to one embodiment of the present invention, the instrumentutilizes a multi-port valve which defines several fluid branches eachassociated with a reagent. The valve has a common inlet and commonoutlet which are selectively brought into fluid communication with thebranches in a controlled sequence. At each branch, there is a two-waythree-port isolation valve which controls introduction of an associatedreagent into the branch. When a branch is selected by the rotary valve,the reagent introduced into the branch is delivered out of the commonoutlet by the flow from the common inlet.

Several such combination of rotary plus isolation valves may be linkedin tandem or in parallel to accommodate a larger number of differentreagents.

According to another embodiment of the present invention, the reagentsare introduced through isolation valves between two multi-port rotaryvalves.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified schematic fluid diagram of an automated nucleicacid synthesis instrument which incorporates the fluid delivery systemin accordance with one embodiment of the present invention.

FIG. 2 is perspective view of the rotary valve used in the fluiddelivery system.

FIG. 3 is a top view of the rotary valve.

FIG. 4 is a schematic diagram illustrating another embodiment of thepresent invention in which isolation valves are positioned between twomulti-port rotary valve.

DETAIL DESCRIPTION OF THE ILLUSTRATED EMBODIMENT

The following description is of the best contemplated mode of carryingout the invention. This description is made for the purpose ofillustrating the general principles of the invention and should not betaken in a limiting sense. The scope of the invention is best determinedby reference to the appended claims.

While the present invention is described in the context of DNAsynthesis, it is to be understood that the present invention can beimplemented for other chemical processes, e.g. peptide and proteinsynthesis, protein sequencing and oligosaccaride synthesis andsequencing, as well as any system requiring integrated delivery ofdifferent reagents.

FIG. 1 illustrates the simplified schematic arrangement of an automatedchemical processing apparatus suitable for use to synthesize DNA. Thisis a simplified fluid diagram for the purpose of illustrating the basicconcept of the invention. A fully automated apparatus typicallycomprises more reagent reservoirs and additional flow components. It iswithin the knowledge of one skilled in the art to incorporate thenecessary reagent reservoirs and flow components to build an automatedDNA synthesizing apparatus which incorporates the present invention inlight of the disclosure of U.S. Pat. No. 4,458,066 to Caruthers et alwhich has been incorporated by reference herein.

Referring to FIG. 1, reservoirs 11 to 21 contain appropriate chemicalreagents for DNA synthesis, e.g. acetonitrile (solvent), tetrazole,oxidizer, capping activators, amidire activator, deblocker, and variousamidites. Each reservoir is capped. Tubings 24 that are unshaded in FIG.1 are gas lines which deliver a pressurized inert gas such as heliumfrom a tank 26 to above the reagent level in each reservoir. Manifolds28 to 30 are provided to distribute the pressurized gas to thereservoirs 11 to 21. Tubings that are shaded in FIG. 1 are for reagenttransport. The tubings 32 have ends immersed in the reagents and areconnected to valves 36, 38, 40, 41 to 48 which turn on and off fluiddelivery from the reservoirs. As will be described in greater detailbelow, some of the tubings 32 are connected to isolation valves 41 to 48which control the flow through the tubings. When an isolation valve isactuated, the reagent in the reservoir connected to that valve will beforced into the connected tubing and through the valve by thepressurized gas. The valve 36 is a normally-closed two port valve. Whenit is actuated, it permits flow through the valve. When it is released,it blocks flow through the valve. The valves 38 and 40 are two-waythree-port valves similar to the isolation valves 41 to 48 describedbelow.

An additional valve 34 is provided at a point in the fluid system whichis connected to the pressurized gas tank 26. When this valve isactuated, gas is injected into the flow stream to interrupt thecontinuity of the chemical reagent flow.

Near the downstream end of the system is a chemical reaction chamber 50which is designed to facilitate the desired chemical reactions to takeplace, in the example described herein, the synthesis of nucleotides.Further downstream is a detector positioned along or adjacent the flowpath to monitor system performance from the passing fluid flow. At thevery end of the flow system, a waste container 54 is provided to collectthe spent reagents that have flowed through the system, or a collectiondevice (not shown) is provided if so desired to collect any reaction endproducts from the chemical reactions.

The control of the delivery of the various reagents to the reactionchamber is effected by a combination of a multi-port rotary valve 56 andseveral isolation valves 41 to 48. Referring also to FIGS. 2 and 3, themulti-port valve 56 has a common inlet 58 and a common outlet 59, and inthe example shown eight pairs of branch inlet ports 61-68 and outletports 71-78 which are coupled to fluid branches 81-88 (see FIG. 1).Rotary valves with more ports may be used depending on the systemrequirements. The valve 56 has a rotary valve element which selectivelybrings the common inlet 58 and common outlet 59 into fluid communicationwith the pairs of branch inlet and outlet ports (61-68, 71-78) in acontrolled sequence (FIG. 1 shows branch 87 being accessed). Themulti-port rotary valve 56 is available from Valco Instruments Co. Inc.in Houston, Tex., U.S.A (part no. CST8P).

In each branch (81-88), there is a two-way three-port isolation valve(41-48) which controls introduction of an associated reagent into thebranch. When one of the isolation valves is actuated, its three valveports are opened, so that flow may occur in any direction through anyport. When the valve is released, only the port connected to theassociated reservoir is closed. The valves are of the electromechanicaltype which are actuated under control by controller 80. The valves areavailable from General Valve Corp. in Fairfield N.J, U.S.A. (part no.2-104-900). The valves 41 to 48 are connected to the inlet and outletports (61-68, 71-78) by tubings 92 and 94 as shown in FIG. 1.

FIG. 1 shows the valve 56 accessing the branch 87. In this position, theflow path from the solvent (acetonitrile) reservoir 11 passes throughvalves 36, 34, 38 and 40, the common inlet 58 of valve 56, the branchinlet port 67, the tubing 94 in branch 87, the isolation valve 47, thetubing 92 in branch 87, the branch outlet port 77, the common outlet 59of valve 56, the reaction chamber 50, to the waste container 54. As therotary valve 56 accesses other branches, the flow path would be throughthose branches in a similar manner.

When a branch (81-88) is selected by the rotary valve 56, the reagentintroduced into the branch is delivered out of the common outlet 59along the flow from the common inlet 58. Specifically, in operation, asolvent 11 (in this example acetonitrile) is supplied through the mainflow to the common inlet 58 of the rotary valve 56 and initially floodsall the branch flow passages 92 and 94 by rotating the valve to eachbranch in sequence. Thereafter, a particular reagent in a reservoir isdelivered to the reaction chamber 50 by the following sequence of steps:first, rotating the valve 56 to select access to the pair of inlet andoutlet ports (6-68, 71-78) associated with the reagent; second, activatethe associated isolation valve (41-48) to introduce the reagent into thefluid branch (81-88) which mixes with the solvent (the on-off valve forthe solvent may be turned off to stop the main flow during reagentintroduction); third, release the isolation valve to stop reagent flow;fourth, pump a quantity of solvent through the fluid branch to displacethe bolus of reagent from the fluid branch to the reaction chamber 50and at the same time flush the fluid branch and the valve element toremove traces of the reagent; fifth, rotate valve 56 to another port foranother reagent. It is noted that the branch last accessed by the rotaryvalve 56 is filled with solvent at the end of delivering the reagent outof the fluid branch.

The rotary valve 56 and the valves 41 to 48 are actuated in appropriatesynchronization to deliver the reagents needed to complete eachsynthesis cycle. The synchronization of valve actuations as well asother system functions are controlled by a programmable controller, thedetail of which is not described herein as one can easily implement thecontrol function given the desired operations to be accomplished.

The aforedescribed configuration eliminates cross contamination betweendifferent reagents. The dead volumes with this type of configuration aresubstantially less than implementations involving discreet valves linkedtogether by means of common fluid ports to provide chemical reagentdelivery to a common reaction site. It is estimated that such aconfiguration with 0.020" I.D. tubing can lead to system dead volumes of50 μL or less. Moreover, in the present configuration, the default orfail safe position (i.e. the branches with isolation valve off in astate filled with solvent) provides a wash circuit, eliminatingadditional steps to implement a system wash function. It has been foundthat the present reagent delivery system configuration accounts for 35to 50% savings in consumption of phosphoramidites than other DNAsynthesizer. Phosphoramidites cost a customer on the order of $250 for 2grams or approximately a two-week supply for a typical user.

It is preferred that the tubings 92 and 94 are smaller in flow diameterthan that of the reagent input tubings 32. This reduces the flow volumein the fluid branch 81-88 so that it takes less solvent for flushing thetubings. It is also preferred that the length of the sections of thetubings 92 and 94 between the isolation valves 41-48 and the respectiveinlet and outlet ports 61-68 and 71-78 are substantially the same. Thisensures that for those reagents introduced to the main flow via therotary valve 56, the distance to reach the reaction chamber 50 isconstant. Further, it is preferred that the length of the sections oftubings 32 leading from the reagent reservoirs 14-21 to the respectiveisolation valves 41 to 48 are substantially the same. In other words,the reagents are arranged in a circular symmetrical configuration withrespect to a central delivery hub (the rotary valve 56). Differences influid path lengths and resistances are eliminated. Control of multiplereagent flow rates and the effects of pressure drop on relative flowrate from the different reagents are normalized by this symmetricalconfiguration. Any drift in fluid flow parameters would be consistentfor the different reagent branches.

The basic configuration described above may be built upon to handlelarger number of different reagents. For example, two or more of suchconfiguration of rotary valve plus isolation valves may be connected inparallel, i.e. sharing one main flow input to the inlets of the rotaryvalves and one or more outputs for multiple reagent delivery site. Also,two or more of such configuration can be linked in tandem wherein theoutput of an upstream rotary valve is the input of a downstream rotaryvalve. Further, two or more of such configuration can be connected in amanner in which one or more of the isolation valves in a rotary valve isreplaced with a rotary valve having associated isolation valves. Stillfurther, the configuration may be used in "reverse" to create multipledelivery sites at the branches with one main reagent input to the rotaryvalve. Conceivably, any combination of the foregoing implementation maybe possible.

Referring to FIG. 4, another embodiment of the present invention isshown which utilizes two rotary valves 96 and 98 and isolation valves101 to 105 connected therebetween. The rotary valves 96 and 98 in thisembodiment can be made simpler than the previous embodiment. The rotaryvalve 96 has a common inlet 107 and several outlets 108. The flow fromthe common inlet 107 is selectively directed to the various outlets 108.The rotary valve 98 is arranged in reverse with respect to flow, i.e.there are several inlets 109 and a common outlet 110. Actually, thevalves 96 and 98 can be exactly the same but one valve is connected inthe flow system in an inverted manner. Isolation valves 101 to 105 areconnected intermediate along the fluid branches 111 to 115 between therotary valves. These isolation valves may be the same as those in theprevious embodiment. Reagent reservoirs are connected to the isolationvalves in a similar manner as before. The overall function of theconfiguration shown in FIG. 4 is similar to the function of the rotaryvalve and isolation valves shown in FIG. 1. By connecting thisconfiguration to the solvent input flow stream (at inlet 58 in FIG. 1)and output flow stream (at outlet 59) to the reaction column 50, reagentdelivery can be effected in a similar manner. Both rotary valves 96 and98 are actuated simultaneously to select a branch for reagent deliveryto the reaction chamber 50, as compared to the previous embodiment wherea single rotary element is actuated to simultaneously access a pair ofports connected to a branch. FIG. 4 shows the rotary valves selectingbranch 113.

While the invention has been described with respect to the illustratedembodiments in accordance therewith, it will be apparent to thoseskilled in the art that various modifications and improvements may bemade without departing from the scope and spirit of the invention.Accordingly, it is to be understood that the invention is not to belimited by the specific illustrated embodiments, but only by the scopeof the appended claims.

I claim:
 1. An apparatus for fluid delivery system comprising:means for supplying a fluid; valve means for selecting flow between common ports, said valve means including a first common port coupled to the supply means, a second common port, a plurality of fluid branches each having two ends in constant flow communication, and means for alternatively selecting fluid flow through a selected fluid branch by connecting flow between the first and second common ports and the two ends of said selected fluid branch, whereby fluid flows through the valve means from the first common port to the second common port through said selected fluid branch; and a plurality of isolation valves each coupled along each fluid branch to one of a plurality of different external fluids, each isolation valve operating to control flow of each external fluid into the respective fluid branches, whereby a desired external fluid is delivered through the second common port by connecting the flow between the first and second common ports and the two ends of the fluid branch which is coupled to said desired external fluid by using the valve means and introducing said desired external fluid into said selected fluid branch by controlling the isolation valve coupled to said selected fluid branch.
 2. An apparatus for fluid delivery system as in claim 1 wherein the valve means is an integrated rotary valve having means for accessing the two ends of the selected fluid branch simultaneously.
 3. An apparatus for fluid delivery system as in claim 1 wherein the valve means comprises first and second valves, the first valve having a common inlet and a plurality of outlets and means for alternatively selecting fluid flow from said common inlet through one of said outlets, the second valve having a plurality of inlets and a common outlet and means for alternatively selecting fluid flow from one of the inlets to the common outlet, whereby each fluid branch is defined between a pair of said plurality of inlets and outlets and the common inlet corresponds to the first common port of the valve means and the common outlet corresponds to the second common port of the valve means, and wherein the isolation valves are each coupled intermediate between a pair of said plurality of inlets and outlets for controlling flow of the external fluid into a selected fluid branch between the first and second valves.
 4. An automated chemical reaction processing instrument comprising:a main fluid supply; valve means for selecting flow between common ports, said valve means including a first common port coupled to said main fluid supply, a second common port, a plurality of fluid branches each having two ends in constant flow communication, and means for alternatively selecting fluid flow through a selected fluid branch by connecting flow between the first and second common ports and the two ends of said selected fluid branch, whereby fluid flows through the valve means from the first common port to the second common port through a selected fluid branch; supply means for supplying different reagents; a plurality of isolation valves each coupled to the supply means and equidistant between the ends of each fluid branch, each isolation valve operating to control flow of each of said different reagents from the supply means into the respective fluid branches, whereby the different reagents are introduced into the respective fluid branches and delivered through the second common port in sequence by connecting flow between the first and second common ports and the two ends of the fluid branches using said valve means and introducing the reagents into the selected fluid branches by controlling the isolation valves; and means for defining a reaction site coupled to the second common port where the different reagents are delivered in a predetermined sequence for carrying out a desired reaction.
 5. An automated instrument as in claim 4 wherein the valve means is an integrated rotary valve having means for accessing the two ends of the selected fluid branch simultaneously.
 6. An automated instrument as in claim 4 wherein the valve means comprises first and second valves, the first valve having a common inlet and a plurality of outlets and means for alternatively selecting fluid flow from said common inlet through one of said outlets, the second valve having a plurality of inlets and a common outlet and means for alternatively selecting fluid flow from one of the inlets to the common outlet, whereby each fluid branch is defined between a pair of said plurality of inlets and outlets and the common inlet corresponds to the first common port of the valve means and the common outlet corresponds to the second common port of the valve means, and wherein the isolation valves are each coupled intermediate between a pair of said plurality of inlets and outlets for controlling flow of the external fluid into a selected fluid branch between the first and second valves.
 7. An automated instrument as in claim 4 wherein flow distances between the isolation valves and the second common port are substantially the same.
 8. An automated instrument as in claim 4 wherein the lengths of the fluid branches are substantially the same.
 9. At automated instrument as in claim 4 wherein the reagents are suitable for nucleic acid synthesis.
 10. An apparatus for fluid delivery system comprising:supply means for supplying a first fluid, valve means for selecting flow between common ports, said valve means having an input common port coupled to the supply means, an output common port, and a plurality of branch output ports and a plurality of branch input ports, each said output port being uniquely associated with an input port and in constant flow communication therewith, said valve means including means for selectively connecting said input common port to any one of said branch input ports and said output common port to any one of said branch output ports; conduit means connecting each of said branch input ports to a respective branch output ports to form a plurality of branches between said input common port and said output common port to allow flow of said first fluid through any one of said branches; and an isolation valve along each of said plurality of branches coupled equidistant between said input ports and output ports, and connected to a respective second fluid, said isolation valve operating to introduce said respective second fluid to the respective branches, whereby any desired one of a plurality of second fluids can be introduced into one of said plurality of fluid branches and delivered through the output common port. 